The very first one in this documentation:
http://www.mathworks.com/help/matlab/matlab_oop/getting-familiar-with-classes.html
The class is:
classdef BasicClass
properties
Value
end
methods
function r = roundOff(obj)
r = round([obj.Value],2);
end
function r = multiplyBy(obj,n)
r = [obj.Value] * n;
end
end
end
When I run it this way
a = BasicClass
a.Value = pi/3;
It works fine and does what it should but this piece of code
a = BasicClass(pi/3);
Gives the following error:
"Error using round
Too many input arguments."
What does it mean? (I'm using R2014a) Is it stupid to use oop in Matlab? LOL
Your error message doesn't look correct compared with the code, whichever your missing a class constructor (as is mentioned at the half way down the help link):
classdef BasicClass
properties
Value
end
methods
% Class constructor -> which you can pass pi/3 into.
function obj = BasicClass ( varargin )
if nargin == 1
obj.Value = varargin{1};
end
end
% Your Methods
function r = roundOff(obj)
r = round([obj.Value],2);
end
function r = multiplyBy(obj,n)
r = [obj.Value] * n;
end
end
end
Related
In the matlab, I defined a class and instantiated the class in another script, but I got different values in and out of the method. My matlab code are shown bellow:
test_add.m
classdef test_add
properties
a
b
end
methods
function obj = test_add(a, b)
obj.a = a;
obj.b = b;
end
function c = add_1(obj)
c = obj.a + 1;
end
function inter(obj, t)
for i = 1:t
obj.a = obj.add_1();
end
fprintf('In the method:\n');
fprintf('a = %d\n',obj.a);
fprintf('b = %d\n',obj.b);
disp('=======================');
end
end
end
main.m
tt = test_add(1,2);
tt.inter(3);
fprintf('Out of the method:\n');
fprintf('a = %d\n',tt.a);
fprintf('b = %d\n',tt.b);
output:
In the method:
a = 4
b = 2
=======================
Out of the method:
a = 1
b = 2
In Matlab there are two type of classes: handle class and Value class. If you said nothing you get the Value class. Most of the OO languages out there are using handle class semantic.
So, you have two options:
Change you class to handle class by inheriting from handle
classdef test_add < handle
Stay with Value class and change your inter function to return obj.
But then, in main call obj=tt.inter(3) to get the updated object.
function obj = inter(obj, t)
for i = 1:t
obj.a = obj.add_1();
end
fprintf('In the method:\n');
fprintf('a = %d\n',obj.a);
fprintf('b = %d\n',obj.b);
disp('=======================');
end
It's a problem of value class vs handle class, the solution is:
test_add.m
classdef test_add < handle
...
end
Then, the output is:
In the method:
a = 4
b = 2
=======================
Out of the method:
a = 4
b = 2
I've created two fairly simple classes in MATLAB, and I have a problem with running this.
classdef A
properties
a
end
methods
function obj = A(a)
obj.a = a;
end
end
end
classdef B
properties
b
end
methods
function obj = B(b)
obj.b = b;
end
end
end
Then, I wrote in the command window:
x = A(1);
y = B(x);
and I got the following error:
Maximum limit of 500 reached.
Why do I get this? And how should I fix it?
I have a class in MATLAB that represents an imaginary number. I have a constructor and two data members: real and imag. I am playing with overloading operator in a class and I want to make it work with matrices:
function obj = plus(o1, o2)
if (any(size(o1) ~= size(o2)))
error('dimensions must match');
end
[n,m] = size(o1);
obj(n,m) = mycomplex();
for i=1:n
for j=1:m
obj(i,j).real = o1(i,j).real + o2(i,j).real;
obj(i,j).imag = o1(i,j).imag + o2(i,j).imag;
end
end
end
But I don't want to use for loops. I want to do something like:
[obj.real] = [o1.real] + [o2.real]
But I don't understand why it does not work... the error says:
"Error in + Too many output arguments".
I know that in MATLAB it is good to avoid for loops for speed up... Can someone explain me why this does not work, and the right way to think about vectorization in MATLAB with an example for my function?
Thanks in advance.
EDIT: definition of my complex class:
classdef mycomplex < handle & matlab.mixin.CustomDisplay
properties (Access = public)
real;
imag;
end
methods (Access = public)
function this = mycomplex(varargin)
switch (nargin)
case 0
this.real = 0;
this.imag = 0;
case 1
this.real = varargin{1};
this.imag = 0;
case 2
this.real = varargin{1};
this.imag = varargin{2};
otherwise
error('Can''t have more than two arguments');
end
obj = this;
end
end
end
Consider the implementation below. First some notes:
the constructor can be called with no parameters. This is important to allow preallocating object arrays: obj(m,n) = MyComplex()
for convenience, the constructor accepts either scalar of array arguments. So we can call: c_scalar = MyComplex(1,1) or c_array = MyComplex(rand(3,1), rand(3,1))
the plus operator uses a for-loop for now (we will later change this).
(Note that I skipped some validations in the code, like checking that o1 and o2 are of the same size, similarly for a and b in the constructor).
classdef MyComplex < handle
properties
real
imag
end
methods
function obj = MyComplex(a,b)
% default values
if nargin < 2, b = 0; end
if nargin < 1, a = 0; end
% accepts scalar/array inputs
if isscalar(a) && isscalar(b)
obj.real = a;
obj.imag = b;
else
[m,n] = size(a);
obj(m,n) = MyComplex();
for i=1:m*n
obj(i).real = a(i);
obj(i).imag = b(i);
end
end
end
function obj = plus(o1, o2)
[m,n] = size(o1);
obj(m,n) = MyComplex(); % preallocate object array
for i=1:m*n % linear indexing
obj(i).real = o1(i).real + o2(i).real;
obj(i).imag = o1(i).imag + o2(i).imag;
end
end
end
end
An example of using the class:
% scalar objects
>> c1 = MyComplex(1,2);
>> c2 = MyComplex(3,4);
>> c3 = c1 + c2
c3 =
MyComplex with properties:
real: 4
imag: 6
% array of objects
>> c4 = [c1;c1] + [c2;c2]
c4 =
2x1 MyComplex array with properties:
real
imag
Now here is a vectorized version of the plus method:
function obj = plus(o1, o2)
[m,n] = size(o1);
obj(m,n) = MyComplex();
x = num2cell([o1.real] + [o2.real]);
[obj.real] = deal(x{:});
x = num2cell([o1.imag] + [o2.imag]);
[obj.imag] = deal(x{:});
end
I'm using the syntax: [objarray.propName] to reference a property in object arrays, this return the values as a vector.
For the opposite of assigning a property in an object array, I use comma-separated lists, thus I had to convert to a cell array to get the x{:} convenient syntax.
Note that the deal call is not strictly needed, we could write the assignment without it:
[obj.real] = x{:};
The line obj(n,m) = mycomplex() looks very suspicious. I think what you want to do there is obj = mycomplex(n,m) instead.
I can't see the rest of your code, but it's miraculous to me that this line even works. I suspect that you have an obj variable stored somewhere already, and this code simply overwrites one entry of that variable. I predict that if you clear all variables, it's going to fail on that line.
Again, it's very difficult to understand what happens without knowing what mycomplex() actually does.
I'm working with classes a long time ago but yet I couldn't get one thing that how to OUTPUT from a function/Constructor of like a function. I have seen multiple examples but coulnd't clear the point. Here I'v a simple example of myFunc outputting an array, and same function in class, How to output from class like a function.
How to take output from any function of class just like a function?
myFunc:
function M=myFunc(n)
[M]=[];
i=0;
for ii=1:n
M(ii)=i;
%% Counter
i=i+4;
end
end
MyClass:
classdef myClass
properties (Access=private)
n
M
i
end
methods
function obj = myClass(n)
obj.n = n;
end
function myFunc(obj)
for ii=1:obj.n
obj.M(ii)=obj.i;
%% Counter
obj.i=obj.i+4;
end
end
end
end
**EDIT 1:**
classdef myClass
properties (Access=private)
n
M
i
end
methods
function obj = myClass(n)
obj.n = n;
end
function M = myFunc(obj)
for ii=1:obj.n
obj.M(ii)=obj.i;
%% Counter
obj.i=obj.i+4;
end
M = obj.M;
end
end
end
A method works just like a normal function, except that the first input of a non-static method is always expected to be a class instance
You call the method defined as
methods
function [out1, out2] = fcnName(object, in1, in2)
% do stuff here (assign outputs!)
end
end
like so:
[out1, out2] = object.fcnName(in1,in2)
or
[out1, out2] = fcnName(object,in1,in2)
Applied to your example:
methods
function M = myFunc(obj)
for ii=1:obj.n
obj.M(ii)=obj.i;
%% Counter
obj.i=obj.i+4;
end
M = obj.M;
end
end
you call myFunc as
obj = myClass(3);
M = myFunc(obj);
Here is my code:
f.m:
classdef f < handle
properties (Access = public)
functionString = '';
x;
end
methods
function obj = f
if nargin == 0
syms s;
obj.x = input('Enter your function: ');
obj.functionString = ilaplace(obj.x);
end
end
function value = subsref(obj, a)
t = a.subs{:};
value = eval(obj.functionString);
end
function display(obj)
end
end
end
test.m:
syms s t;
[n d] = numden(f.x); % Here I want to use x, which is the user input, How can I do such thing?
zeros = solve(n);
poles = solve(d);
disp('The Poles:');
disp(poles);
disp('The Zeros:');
disp(zeros);
disp('The Result:');
disp(z(t));
disp('The Initial Value:');
disp(z(0));
disp('The Final Value:');
disp(z(Inf));
When I type test in the command window, it tells me the following:
>> test
??? The property 'x' in class 'f' must be accessed from a class instance because it
is not a Constant property.
As Alex points out, you need an instance of f to access the member property x, like so:
myf = f();
f.x
You do not need an accessor method to get at x as it is defined as a public property. If you chose to make x private, then you'd need an accessor method something like this:
function x = getX( obj )
x = obj.x;
end